Natural or by Vaccination, COVID-19 Immunity Lasts a Year
Researchers from Sweden’s Karolinska Institute, Uppsala University, KTH Royal Institute of Technology, Centre for Infectious Medicine, and Public Health Agency have recently published a study that looked at neutralizing antibody titers against wild-type COVID-19 and its several strains people who had either been infected with mild SARS-CoV-2 a year before or vaccinated, and discovered a reduced neutralization capacity against some virus variants.
In the study, a separate group of people hadn’t yet received a vaccine and had mild Coronavirus the previous year.
The researchers note that initially neutralizing antibodies and high levels of circulating COVID-19 spike protein IgG decline over a few months, finally stabilizing at a somewhat stable level, similar to other reports on the long-term potency neutralizing antibodies induced by vaccines and past infection.
Wild-type spike IgG was discovered in 91% of individuals after four months, 84% after eight months, and 80% after 12 months, and wild-type neutralizing antibodies in 96% of individuals after four, in 93% after eight, and in 91% after 12 months.
The researchers evaluated the neutralization capacity of sera obtained from people who had been exposed to COVID-19 a year before against wild-type Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (Delta) variants of concern, finding only a modest decrease in effectiveness against the Alpha and Delta strains.
The Beta and Gamma strains, on the other hand, showed a more dramatic reduction in neutralizing capacity. When compared to the wild type, any vaccine type showed a similar decrease of effectiveness against the Beta and Gamma strains among the vaccinated participants.
There have been few reports of mutations in the Coronavirus spike protein that change the structure to limit neutralizing antibody affinity.
Mutations that boost the spike protein’s affinity for the ACE2 receptor, as seen in various stains, like the Delta strain, can greatly increase the transmissibility of the virus by increasing the likelihood of cell entry.
Overall, the immunity obtained by prior infection and vaccination remained strong a year later, especially against wild-type COVID-19 and the now-common Alpha and Delta variants, while effectiveness against the later-emerging Beta and Gamma strains was fading.
Furthermore, the next generation of COVID-19 vaccines will need to be future-proofed against possible new mutations.
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